Great idea, Andy, but we're talking 55,000 lines of code.
If the app attracts commercial backing, the problem of code language will be addressed.
Right now, I am checking out whether I can as you suggest, install VB6 on a W7 machine. In spite of 2 "known compatibility issues" warnings, it [MS VB6 Professional Edition, purchased in ~ 1998] installed without apparent problems. I am able to load my app and there are surprisingly few issues, which I am now addressing. Until I fix these, it won't run. I'll let you know how it works out.
I appreciate your feedback@